diff --git a/cep/transferencia.py b/cep/transferencia.py
index cd3f469..c3861e4 100644
--- a/cep/transferencia.py
+++ b/cep/transferencia.py
@@ -4,9 +4,16 @@
 
 import clabe
 from lxml import etree
+from requests import HTTPError
 
 from .client import Client
 from .cuenta import Cuenta
+from .exc import CepError, MaxRequestError
+
+MAX_REQUEST_ERROR_MESSAGE = (
+    b'Lo sentimos, pero ha excedido el número máximo '
+    b'de consultas en este portal'
+)
 
 
 @dataclass
@@ -36,7 +43,15 @@ def validar(
         )
         if not client:
             return None
-        xml = cls._descargar(client, 'XML')
+
+        try:
+            xml = cls._descargar(client, 'XML')
+        except HTTPError as exc:
+            raise CepError from exc
+
+        if MAX_REQUEST_ERROR_MESSAGE in xml:
+            raise MaxRequestError
+
         resp = etree.fromstring(xml)
 
         ordenante = Cuenta.from_etree(resp.find('Ordenante'))
diff --git a/cep/version.py b/cep/version.py
index 124e462..4c9f88d 100644
--- a/cep/version.py
+++ b/cep/version.py
@@ -1 +1 @@
-__version__ = '0.1.7'
+__version__ = '0.2.0.dev0'
diff --git a/requirements-test.txt b/requirements-test.txt
index 9b43c9c..d55fe2b 100644
--- a/requirements-test.txt
+++ b/requirements-test.txt
@@ -1,7 +1,7 @@
 pytest==6.2.5
 pytest-vcr==1.0.2
 pytest-cov==3.0.0
-black==21.12b0
+black==22.3.0
 flake8==4.0.1
 isort[pipfile]==5.10.1
 mypy==0.790
diff --git a/tests/test_transferencia.py b/tests/test_transferencia.py
index 206e5c1..5cbea57 100644
--- a/tests/test_transferencia.py
+++ b/tests/test_transferencia.py
@@ -2,8 +2,10 @@
 import os
 
 import pytest
+from requests import HTTPError
 
 from cep import Transferencia
+from cep.exc import CepError, MaxRequestError
 
 
 @pytest.mark.vcr
@@ -54,3 +56,36 @@ def test_descagar_transferencia_con_fecha_distinta(transferencia):
     )
     assert type(tr.to_dict()) is dict
     tr.descargar()
+
+
+@pytest.mark.vcr
+def test_lanza_cep_error_para_errores_500():
+    try:
+        for i in range(10):
+            Transferencia.validar(
+                fecha=dt.date(2022, 4, 19),
+                clave_rastreo='CUENCA927820173168',
+                emisor='90646',  # STP
+                receptor='40012',  # BBVA
+                cuenta='012180000',
+                monto=0.01,
+            )
+    except CepError as exc:
+        assert type(exc.__cause__) is HTTPError
+        assert str(exc.__cause__) == (
+            '500 Server Error: Internal Server Error for url: '
+            'https://www.banxico.org.mx/cep/descarga.do?formato=XML'
+        )
+
+
+@pytest.mark.vcr
+def test_maximo_numero_de_requests():
+    with pytest.raises(MaxRequestError):
+        Transferencia.validar(
+            fecha=dt.date(2022, 4, 19),
+            clave_rastreo='CUENCA927820173168',
+            emisor='90646',  # STP
+            receptor='40012',  # BBVA
+            cuenta='012180000',
+            monto=0.01,
+        )